The hydroxide of which metal ion(s) which is/are soluble in excess of NaOH solution

Options

A. `A1^(3+)`
B. `Zn^(2+)`
C. `Fe^(3+)`
D. `Cu^(2+)`

Explanation

To determine which metal ions have hydroxides that are soluble in excess NaOH solution, we can follow these steps:

### Step 1: Identify the Metal Ions
The metal ions given in the question are:
1. Aluminium (Al³⁺)
2. Zinc (Zn²⁺)
3. Iron (Fe³⁺)
4. Copper (Cu²⁺)

### Step 2: Understand Amphoteric Hydroxides
Amphoteric hydroxides are those that can react with both acids and bases. This property allows them to dissolve in excess NaOH, forming soluble complex ions. The amphoteric hydroxides among the given metal ions are:
- Aluminium hydroxide (Al(OH)₃)
- Zinc hydroxide (Zn(OH)₂)

### Step 3: Reactions with Excess NaOH
Now, we will write the reactions of the amphoteric hydroxides with excess NaOH:

1. **Aluminium Hydroxide Reaction:**
\[ \text{Al(OH)}_3 + \text{NaOH (excess)} \rightarrow \text{NaAlO}_2 + \text{H}_2\text{O} \]
- Here, sodium aluminate (NaAlO₂) is formed, which is soluble in water.

2. **Zinc Hydroxide Reaction:**
\[ \text{Zn(OH)}_2 + \text{NaOH (excess)} \rightarrow \text{Na}_2\text{ZnO}_2 + \text{H}_2\text{O} \]
- Here, sodium zincate (Na₂ZnO₂) is formed, which is also soluble in water.

### Step 4: Non-Amphoteric Hydroxides
For the other two metal ions:
- **Iron Hydroxide (Fe(OH)₃)** and **Copper Hydroxide (Cu(OH)₂)** do not dissolve in excess NaOH. They form insoluble precipitates:
- Iron(III) hydroxide is reddish-brown and insoluble.
- Copper(II) hydroxide is blue and also insoluble.

### Conclusion
The hydroxides of the metal ions that are soluble in excess NaOH solution are:
- **Aluminium (Al³⁺)**
- **Zinc (Zn²⁺)**

### Final Answer
The hydroxides of Aluminium and Zinc are soluble in excess NaOH solution.

---